Process of reducing metallic oxids.



UNITED STATES.

PATENT orinon.

FREDERICK M. BECKET, OF NIAGARA FALLS, NEW YORK, SSIGNOR TO ELECTRO METALLURGICAL COMPANY, A CORPORATION OF EST VIR- GINIA.

PROCESS OF REDUCING METALLIC OXIDS;

Specification of Letters Patent.

Patented May 21, 1907.

Application filed se tember 23, 1905- Serial No. 279,857.

To all 1072,0711, it may concern- Be t known that I, FREDERICK M. BECKET,

"a subject of the King of Great Britain, residing at Niagara Falls, in the county of Niagara and State of New York, have invented certain new and useful Improvements in Processes of Reducing Metallic Oxids, of which the following is a specification.

his invention is a process for the production of metals and alloys of low silicon and carbon content, and is more particularly applicable to the metals chromium, tungsten, molybdenum and vanadium and to the alloys of these metals with iron or nickel.

The invention consists in reducing a suitable oxid or oxygen-containing compound or mixture of oxids by silicon, the silicon being used in proportions and under conditions to insure a low silicon content of the product. The conditions necessary for substantially complete reduction of the refractory metallic oxid or oxids above mentioned and the prod uction of metals or alloys of low silicon and carbon content are obtainable so far as known only in an electric furnace. Preferably a basic flux is used to combine with the silica derived from the oxidation of the silicon.

Metallurgists have long been familiar with the reducing action of silicon on certain metallic oxids, such as oxid of iron, and advantage is taken of this chemical reaction in many industries,-for example in the manu facture of steel. In these cases the silicon exists in the form-of an alloy, its reducing properties are employed as a means of eliminating it from the finished product rather than as a means of producing further quantities of metal, and the proportion of reducible oxid used for its remo'val is largely in excess of that theoretically i'iecessary. In the form of metallic silicides, silicon is employed to reduce metallic oxids dissolved in molten metals, and in this form it is also used or the production of double silicides of the metals, and of alloys containing considerable .-ropor tions of silicon. Until a comparatively recent date metallic silicon has not been considered an article of commerce. The metal is now produced in the electric furnace, often associated with considerable quantities of iron, at such cost and in such quantity as to permit its economical application as a reduc ing agent in certain electro-metallurgical operations.

l I have found that silicon, although not so I electropositive as aluminium, may be advantageously employed in the electric furnace as a reducing agent in the production of chromium, molybdenum, tungsten and vanadium, or the iron or nickel alloys of these metals. When a suitable mixture consisting of silicon, an oxid of one or more of the above metals, and a basic flux is treated in an elec tric'fur'nace, the advantages of a continuous and very rapid process may be obtained, and by suitably proportioning the ingredients of the charge the silicon content in the reduced metals maybe made as smallas 0.01 percent. or less.

As a specific example of the process I will describe its application to the mamifacture of low carbon and low silicon ferrochromium from chromite. As the chromium in chromite exists as chromium sesquioxid, Cr O,, and practically all the iron as ferrous oxid, FeO; the following reactions take place.

A fair commercial grade of chromite contains 52 percent. Cr,(), and 16 percent. FeO, and 100 pounds of this ore will therefore require, according to the above reactions, 17.7 pounds silicon for complete reduction of the chromium and iron. Arepresentative analy sis of ferrochromium made by this method is as follows: Chromium 71.00 percent; iron 28.40 percent; carbon 0.50 percent; silicon 0.10 percent.

It is advantageous to use the silicon in a fairly fine state of division and the metal is generally crushed so that it will all pass a ten-mesh screen. However, the state of division of the silicon depends on the scale of the operation. The use of a basic flux in the production of ferrochromium is not essential although advantageous. Most commercial chromites contain from S to 15 percent. A1 0 and 8 to 15 percent. MgO. These materials serve as basic flux for the silica present in the ore and for that produced by oxidation of the silicon; but the proportions are such that to maintain this slag fluid for tapping, a higher temperature is necessary than that required for complete reduction of the chromium and iron oxids by silicon.

By mixing chromite and silicon in practil cally theoretical proportions, together with withdrawn as desired.

some basic flux such as lime, and bringing the mixture to a stateof fusion in an electric furnace, a very high yield of chromium and iron may be obtained from the ore used and the alloy contains only fractions of a percent. of carbon and silicon. It is not essential that the proportions be precisely those indicated by theory, because in the casein which very low silicon content is required in the alloy, (less than 0.2 percent.), the chromite is used in very slight excess of the theroetical proportions; and in the case in which a silicon content as high as one percent. may be permitted, the silicon is used in very slight excessf There'is slight advantage in the latter method on account of the fact that the yield of metal from the ore is slightly higher. In both cases, however, the variations from the theoretical proportions are small and the yields high.

I do not limit myself to any particular type of electric furnace but I have found it advantageous to carry on the reduction continuously in an electric furnace in which the' current passes through, a molten bath of a mixture of ore, silicon and flux, and from whlch part or all of the metal or slag may be a mixture of silicon and oxid or oxygen containing compound of the metals referred to and not effect complete reduction; and to obtain a high yield of the desired metal or alloy and to insure a low silicon content therein, I have found it advantageous to feed the mixture to a bath which is constantly maintained at a temperature higher than that necessary to cause some reaction.

The electric furnace operation may be earriedout by fusing the ore and flux and-then adding thereto the metallic silicon, or by fusing a mixture of ore and silicon and adding flux to this bath from time to time, but I have not found these methods to be as eflicient as that above described. 7

As the reaction betweensilicon and the above mentioned metallic oxids is strongly exothermic, a relatively small amount of electrical energyis requi dfor the reduction; moreover the react on: 'i'oceeds without evolution of gas whieh 'i'is i great practical advantage. Thc'use of silicon as a reducing .agent is highly advantageous in practice as compared with the use ofaluminium for several reasons among which may be mentioned the relatively large weight of metal which is separated per unit weight of the reducing agent the comparative ease'yvith which silicon is obtained a fine state of division whereby a more intimate mixture is obtainable; the fact that with such mixtures the reaction proceeds more quietl'y and' wi thless loss of material; and more particularlybecause silicious ores, which are relatively inexpensive, may be successfully used. Aluminium reduces silicon from the silica in- It is possible to melt variably present in such ores as chromite, wolframite, etc., and I have found in practice that silicon so reduced, as well as portions of the aluminium fused for reduction, alloy with the reduced metal, thereby necessitating either a costly selection of ores or other expensive method in case a product low in silicon is required. Furthermore in such case there is liability to the introduction of both silicon and aluminium into the metal, and in practice it is found to be more difficult to eliminate small percentages of the latter metal than of the former.

the reaction not being of a self-propagating character.

I claim 1. The process of reducing refractory metallic oxids which consists in smelting a charge containing a metallic oxid reducible by silicon and silicon, the silicon being present in substantially the proportion required to combine with the oxygen of said oxid whereby a substantially complete oxidation of the silicon is secured and a product low in' silicon is obtained, substantially as described.

2. The process of reducing metallic oxids which consists in electrically smelting acharge containing a metallic oxid reducible by silicon and silicon, the silicon being present in substantially the proportion required to combine with the oxygen of said oxid whereby a substantially complete oxidation of the silicon is secured and a product low in silicon is obtained, substantially as described.

3. The process of reducing refractory metallic oxids which consists in smelting a charge containing a metallic oxid reducible by silicon, silicon and a basic flux, the silicon being present in substantially the proportion required to combine with the oxygen of said oxid whereby a product low in silicon is oboxid whereby a product low in silicon is ob'.

tained, substantially as described.

5. The process of reducing metallic oxids which consists in passing an electric current through a molten bath containing a metallic oxid reducible by silicon and silicon, the silicon being present in substantially the proportion required to combine with the oxygen of said oxid whereby a product low in silicon is obtained, substantially as described.

6. The process of reducing metallic oxids which consists in passing an electric current 10 inn a metallic oxid,

through a molten ba'thcontaining a metallic oxid, reducible by silicon silicon and a basic flux, the silicon being present in substantially the proportion required to combine with the oxygen of said oxid whereby a product low in silicon 1s obtained, substantially as described.

7. The continuous process of reducingme- 1 tallic oxlds which consists in passing an eleca molten bath containtric current through reducible by silicon s1h con and a basic flux, adding fresh portions of the charge and Withdrawing the products as required, substantially as described.

In testimony whereof, I afiix my signature in presence of two witnesses.

FREDERICK M. BECKET.

\Vitnesses:

J AS. H. "IIITING, WM. L. IIEIM. 

